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Studies to establish the safety of middle ear pellets using auditory brainstem response, cytocochleograms and histology

Presenting Author: Emma Hoskison

Published online by Cambridge University Press:  03 June 2016

Emma Hoskison ,
Mat Daniel ,
Mike Mulheran ,
David Furness ,
Roger Bayston  and
John Birchall
Emma Hoskison
Affiliation:
City Hospital, Birmingham
Mat Daniel
Affiliation:
Nottingham University Hsopitals
Mike Mulheran
Affiliation:
University of Leicester
David Furness
Affiliation:
Keele Univertiy
Roger Bayston
Affiliation:
Nottingham University
John Birchall
Affiliation:
Nottingham University
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Abstract

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Learning Objectives: Otitis Media with Effusion (OME) is the commonest cause of paediatric hearing impairment globally. Primary treatment is ventilation tube insertion with a 25% recurrence rate. Antibiotic laden pellets placed in the middle ear present a potential novel treatment strategy. This study aims to establish the safety of these pellets in vivo.

Introduction: Otitis Media with Effusion (OME) is the commonest cause of paediatric hearing impairment globally (Mandel et al 2008). Primary treatment is ventilation tube insertion (NICE Guidelines 2008) with a 25% recurrence rate (Gates et al 1987). Antibiotic laden pellets placed in the middle ear present a potential novel treatment strategy. This study aims to establish the safety of these pellets in vivo.

Methods: Rifampicin and Clindamycin loaded pellets made of poly lactic-co-glycolic acid were surgically placed in guinea pig middle ears. Auditory Brainstem Responses (ABRs) between 8–30 kHz were tested over 16 weeks. ABR thresholds, amplitudes and latencies were measured to assess for ototoxicity; cytocochleograms to identify any cochlea hair cell loss and middle ear histology carried out for evidence of inflammation.

Results: At one week post insertion of antibiotic laden pellets marked ABR threshold elevation (15–40 dB) was observed (P < 0.002–0.0001) against control groups. Persistent significant elevation (25–40 dB) was apparent at 8 and 30 kHz at week 16 with some partial mid frequency recovery. No significant changes in ABR wave amplitudes and latencies were seen. Representative cytocochleograms did not exhibit frank hair cell loss and middle ear histology revealed pellet remnants causing a moderate inflammatory response at 16 weeks.

Conclusions: This novel pattern of threshold elevation in the absence of frank hair cell loss has not been reported previously. The lack of significant changes in ABR latency and amplitude suggests the ototoxic effects are localised to the inner ear without accompanying neurotoxicity. Clinically, this study suggests that rifampicin and clindamycin laden pellets may not be safe to treat OME in vivo.

Learning Objectives: This study demonstrates that middle ear pellets laden with rifampicin and clindamycin cause an ABR threshold elevation and middle ear inflammatory response in guinea pig animal models.